Staged single venturi carburetor

ABSTRACT

A downdraft type carburetor induction passage has a throttle valve above which is a coaxially mounted flow controlling member consisting of a fixed area venturi integrated with a movable venturi bypass valve member to provide high fuel metering signals at low air flows and high air flow potential for wide open throttle operation.

Moore ..26l/DIG. 56

O Unlted States Patent 1 1 1111 3,715,108 Denton 1451 Feb. 6, 1973 [541 STAGED SINGLE VENTURI 3,628,773 12 1971 Kehoe et al ..26I/50 A CARBURETQR 3,680,846 8/1972 Bickhaus etal. ..26l/D1G. 56

[75] Inventor: Ronald T. Denton, Birmingham, FOREIGN PATENTS OR APPLICATIONS 1 30,791 3/1904 Switzerland ..26l/DIG. 56 [73] Assignee: Ford Motor Company, Dearbgm, 200,994 7/1923 Great Britain ..26l/DIG. 56

Mich. Primary Examiner-Tim R. Miles; [22] plied May 1971 Att0rneyJohn R. Faulkner and Robert E. McCollum [21] Appl. No.: 141,181

[57] ABSTRACT 52 us. c1. ..26l/50 A, 26l/DIG. 56 A downdraft type carburetor induction Passage has a 51 Int. Cl ..F02m 9/08 valve abve which is a coaxially "wumed flow [58] Field of Search "261/50 A DIG 56 60 controlling member consisting of a fixed area venturi integrated with a movable 'venturi bypass valve [56] References Cited member to provide high fuel metering signals at low air flows and high air flow potential for wide open UNITED STATES PATENTS throttle operation 1,212,986 1/1917 9 Claims, 1 Drawing Figure STAGED SINGLE VENTURI CARBURETOR This invention relates, in general, to the construction of a carburetor for a motor vehicle type internal com bustion engine. More particularly, it relates to a carburetor having a low silhouette and of the dual stage type.

The lower hood lines on present automobiles and the predicted yet lower hood lines require some modification in the designs of carburetors so that they can continue to be installed on top of the internal combustion engine without interference from the vehicle hood, and yet supply the air flow requirements of the engine. With some engines, a dual stage type carburetor generally is desirable, the first stage providing high fuel metering signals at low air flows, a second stage assuring adequate air flow volume at the higher engine per formance range.

Most carburetors meeting the above requirements require either separate throttle bores or induction passages, or if a single passage is provided, a considerable height to the passage. For a single bore, the primary stage of the carburetor generally requires a fixed area venturi section with one or more concentrically mounted booster venturies to provide the desired fuel metering signals at low air flows. The conventional throttle valve generally is located posterior of the venturi section. The secondary stage would be mounted above the venturi section and controlled by an air valve or similar device. In order to provide the primary air flow, an additional air inlet to the venturi generally would be necessary since in most instances the air valve would remain closed below a certain flow volume.

The above indicates that a single throttle bore, dual stage carburetor would be considerably higher than would be desirable for installation on a conventionallyshaped engine in vehicles with low hood lines.

It is a primary object of the invention, therefore, to provide a low silhouette dual stage carburetor with two stages of flow providing high fuel metering signals at low air flows and high air flow potential at wide open throttle position.

It is another object of the invention to provide a low silhouette carburetor in which a fixed area venturi is integrated with a movable air flow controlling valve member.

It is still another object of the invention to provide a dual stage carburetor construction that comprises a single induction passage in which is mounted a sleeve-like member having an outer profile of a portion ofa venturi, the internal space of the sleeve being closed or opened by a valve member to control the air flow volume to the engine.

Other objects, features and advantages of the invention will become more apparent upon reference to the succeeding detailed description thereof, and to the drawing illustrating a preferred embodiment thereof; wherein the FIGURE schematically illustrates a cross sectional view of a portion of a downdraft carburetor incorporating the invention.

The FIGURE illustrates a portion of the body of a downdraft type carburetor generally used in connection with a motor vehicle internal combustion engine.

The body includes a large diameter central bore 11 of essentially constant cross-sectional area, which defines a conventional induction passage 12. it is open at its upper end to air essentially at atmospheric pressure. lts lower end is adapted to be connected to the intake manifold of the engine so as to subject the passage to the varying manifold vacuum.

The main control of flow through passage 12 is provided by a plate type throttle valve 14 that is fixed to a shaft 16 rotatably mounted in the walls of the body 10, in a manner not shown. Throttle valve 14 is rotatable from the full line position 16 shown, essentially blocking the main flow of air and fuel through passage 12, to the essentially wide open throttle dotted line position 18.

Located above throttle valve 14 is a profiled sleeve member 20 supported from body 10 by a number (only one shown) of struts 21. The outer peripheral surface 22 of member 20 is generated in the shape of one-half of a venturi, and is adapted to cooperate with the adjacent walls 24 of passage 12 so that together surfaces 22 and 24 form a small fixed throat area venturi section 25.

Concentrically located within sleeve 20 is an air flow controlling valve member 26. The latter is fixed on a shaft 27 rotatably mounted in the walls of body 10 in essentially the same manner as throttle valve shaft 16. It is offset at one end as shown so as to nest with the end of throttle valve 14 when both are in the essentially vertical dotted line positions. This offers a minimum of resistance to flow through passage 12.

The primary fuel in this case is adapted to be discharged through an annular slot 28 in the peripheral portion 22 of the sleeve 20, the slot being located at or adjacent the throat 29 of the venturi defined between surfaces 22 and 24. The fuel discharge port 28 in this case is shown connected to a main fuel bowl 30 through a conventional main discharge metering jet 32, a main fuel bowl well 34 with an emulsifying tube 35, a connecting chamber 36, and passage 38. A conventional high speed air bleed 39 is also provided. Additional fuel volume for secondary stage operation is provided by a metering jet 41 controlled by a metering rod 43. The latter would be connected to valve member 26, by suitable means not shown, such that rotation of valve member 26 to increase air flow also raises metering rod 43 to increase fuel flow.

The counterclockwise movement of air valve member 26 to increase the air flow may be made by any known means. In this case, it is accomplished by a vacuum controlled servo 40. The latter is mounted on the carburetor, and has a conventional shell 42 with a hollow interior. The latter is divided into an atmospheric air chamber 44 and a vacuum chamber 46 by an annular flexible diaphragm 48.

The diaphragm 48 is fixed to a lever 50 pivotally offset connected at 52 to valve member 26. A spring 53 I normally biases the diaphragm 48,. rod 50, and valve 26 to the full line closed position. shown. The servo vacuum chamber 46 is connected by a vacuum line 54 to an induction passage port 56 between member 26 and throttle valve 14.

Other details of construction and operation of the carburetor are not shown since they are known and believed to be unnecessary for an understanding of the invention. The carburetor could, for example, use a conventional idle system in which fuel would be drawn from the well 30 to a discharge port below the closed position of throttle valve 14 so as to supply engine idling speed fuel when the throttle is in its closed speed position.

In operation, with throttle valve 14 in its essentially closed position 16 shown, there will be essentially no flow of fuel from the discharge nozzle 28 or any air flow past the throttle valve 14. All fuel and air flow at this time will pass into the engine by way of the idle system, not shown. Both servo chambers 46 and 44 will be at atmospheric pressure, and, therefore, air valve 26 will be in the closed position shown.

As soon as throttle valve 14 is rotated counterclockwise slightly, air flow through the venturi begins, providing a high metering signal at discharge nozzle 28. This draws fuel from the main well and discharges it into the passage 12, in a known manner. The fixed small area of the venturi provided by the stationary surfaces 22 and 24 provides a finite schedule of flow of fuel at these times.

The vacuum signal at this time at port 56 will be low, and the force of servo spring 53 is chosen such that member 20 will remain in the position shown until the throttle valve 14 has rotated counterclockwise approximately 40, for example. At this point, the vacuum level at port 56 will be high enough to actuate the servo and begin moving the air valve 26.

As the throttle valve 14 progresses, therefore, towards a wide open position 18, the increase in manifold vacuum signal acting on servo 40 will begin to rotate the valve 26 so as to progressively increase the air flow through passage 12. This action continues until the throttle valve 14 reaches the wide open throttle position 18, at which time the member 26 will have rotated to its dotted line position 58. Thus it will be seen that the member 26 provides a maximum air flow potential by its rotation to a nearly vertical position.

From the foregoing, therefore, it will be seen that the invention provides not only a low silhouette carburetor for use with low vehicle hood lines, but also one that provides dual stages of air flow operation with high venturi fuel metering signals at low air flows and high air fiow potentials.

I claim:

1. A low silhouette dual flow stage carburetor having an air/fuel induction passage open at one end to air essentially at atmospheric pressure and adapted to be connected to an engine intake manifold at its other end, a throttle valve rotatably mounted in said passage for movement between closed and wide open positions to control flow through said passage, a sleeve-like fuel and air flow control member mounted anterior of said valve and spaced from the walls of said passage, said member having an outer annular arcuate contour of a profile so as together with the walls of said passage define a fixed area venturi, a valve member concentrically mounted within the hollow interior of said member and movable between positions closing or opening the said interior of said member, a fuel nozzle opening into said passage at a point adjacent said venturi so as to be subject to the varying pressure signal therein for the flow of fuel at times therefrom into said passage, said valve member in its closed position defining an initial stage flow at low throttle valve angle positions and low air flows providing a high venturi fuel metering signal, movement of said valve member to a second stage wide open throttle valve position providmg high air flow through said passage, and means to move said valve member.

2. A carburetor as in claim 1, said fuel nozzle comprising a peripheral discharge slot in the surface of said member.

3. A carburetor as in claim 1, the peripheral surface of said sleeve-like member having a semi-torodial like profile of essentially a semi-venturi.

4. A carburetor as in claim 1, said valve member having a recessed portion receiving an edge of said throttle valve in a nested manner upon rotation of said valve to its wide open position and rotation of said valve member to its maximum air flow position.

5. A carburetor as in claim 1, said induction passage having an essentially constant cross-sectional area throughout its length.

6. A carburetor as in claim 1, said fuel nozzle opening into the throat of said venturi.

7. A carburetor as in claim l,'said member being coaxially mounted within said passage.

8. A carburetor as in claim 1, including means operatively acting on said valve member effecting opening movement of said valve member in response to rotation of said throttle valve beyond a predetermined angle.

9. A low silhouette dual flow stage carburetor having an air/fuel induction passage open at one end to air essentially at atmospheric pressure and adapted to be connected to an engine intake manifold at its other end, a throttle valve rotatably mounted in said passage for movement between closed and wide open positions to control flow through said passage, a fuel and air flow control member mounted anterior of said valve and spaced from the walls of said passage, said member having an outer annular arcuate contour of a profile so as together with the walls of said passage constituting a fixed area venturi, said member also constituting an air valve movable between positions to control the flow past said member, a fuel nozzle opening into said passage at a point adjacent said venturi so as to be subject to the varying pressure signal therein for the flow of fuel at times therefrom into said passage, said air valve in a closed position defining an initial stage flow at low throttle valve angle positions and low air flows providing a high venturi fuel metering signal, movement of said valve to a second stage wide open throttle valve position providing high air fiow through said passage, and means to move said valve. 

1. A low silhouette dual flow stage carburetor having an air/fuel induction passage open at one end to air essentially at atmospheric pressure and adapted to be connected to an engine intake manifold at its other end, a throttle valve rotatably mounted in said passage for movement between closed and wide open positions to control flow through said passage, a sleeve-like fuel and air flow control member mounted anterior of said valve and spaced from the walls of said passage, said member having an outer annular arcuate contour of a profile so as together with the walls of said passage define a fixed area venturi, a valve member concentrically mounted within the hollow interior of said member and movable between positions closing or opening the said interior of said member, a fuel nozzle opening into said passage at a point adjacent said venturi so as to be subject to the varying pressure signal therein for the flow of fuel at times therefrom into said passage, said valve member in its closed position defining an initial stage flow at low throttle valve angle positions and low air flows providing a high venturi fuel metering signal, movement of said valve member to a second stage wide open throttle valve position providing high air flow through said passage, and means to move said valve member.
 1. A low silhouette dual flow stage carburetor having an air/fuel induction passage open at one end to air essentially at atmospheric pressure and adapted to be connected to an engine intake manifold at its other end, a throttle valve rotatably mounted in said passage for movement between closed and wide open positions to control flow through said passage, a sleeve-like fuel and air flow control member mounted anterior of said valve and spaced from the walls of said passage, said member having an outer annular arcuate contour of a profile so as together with the walls of said passage define a fixed area venturi, a valve member concentrically mounted within the hollow interior of said member and movable between positions closing or opening the said interior of said member, a fuel nozzle opening into said passage at a point adjacent said venturi so as to be subject to the varying pressure signal therein for the flow of fuel at times therefrom into said passage, said valve member in its closed position defining an initial stage flow at low throttle valve angle positions and low air flows providing a high venturi fuel metering signal, movement of said valve member to a second stage wide open throttle valve position providing high air flow through said passage, and means to move said valve member.
 2. A carburetor as in claim 1, said fuel nozzle comprising a peripheral discharge slot in the surface of said member.
 3. A carburetor as in claim 1, the peripheral surface of said sleeve-like member having a semi-torodial like profile of essentially a semi-venturi.
 4. A carburetor as in claim 1, said valve member having a recessed portion receiving an edge of said throttle valve in a nested manner upon rotation of said valve to its wide open position and rotation of said valve member to its maximum air flow position.
 5. A carburetor as in claim 1, said induction passage having an essentially constant cross-sectional area throughout its length.
 6. A carburetor as in claim 1, said fuel nozzle opening into the throat of said venturi.
 7. A carburetor as in claim 1, said member being coaxially mounted within said passage.
 8. A carburetor as in claim 1, including means operatively acting on said valve member effecting opening movement of said valve member in response to rotation of said throttle valve beyond a predetermined angle. 